This is the typical configuration of prior art devices, which are typically used both on boats and on aircrafts for trim control.
Particularly, many boats currently use trim tabs mounted to the transom for trim control during navigation. Trim tabs, which are also known as “stabilizers”, “trim controls” or “flaps” are movable plate-like extensions of the hull, usually made of metal, that are hinged to the transom flush with the keel and driven by one or more cylinder actuators to variously tilted positions relative to the keel.
Like in aircraft flaps, appropriate control of boat trim tabs provides control of the hydrodynamic force which tends to lift the stern, and consequently lower the bow and cause listing, thereby ensuring the ideal attitude for navigation in a variety of conditions.
Therefore, these trim control systems are widely used in boats and disclosed in various prior art documents, such as Patent Application U.S. Pat. No. 8,047,152 by the same Applicant.
As disclosed in this document, in prior art devices the actuator is attached to the tab by means of the lower bracket which includes a “fork-shaped” element, engaging with the terminal element of the actuator due to the presence of transverse holes that accommodate a pin.
The pin prevents translation between the actuator and the tab and allows the tab to rotate about an axis of rotation perpendicular to the longitudinal axis of the actuator.
Nevertheless, this arrangement is affected by problems and failures.
It the actuator and the tab are not properly mounted to the transom, e.g. in case of misalignment of the actuator and the blade, the rotation of the tab causes unexpected wear or failures, as one part of the fork-shaped element is more stressed than another.
Improper mounting is a rather likely event, as such mounting requires quite a complex procedure.
At first the tab has to be mounted as an ideal extension of the keel line, then the hinge and the actuator are attached such that the latter is perfectly perpendicular to the plane defined by the tab.
Then, the actuator is attached to the transom.
Mounting errors are clearly possible, especially due to the presence of the fork-shaped element, which inevitably has some clearance and does not allow proper inclination of the actuator.
The offset between the actuator and the tab is inevitable and causes malfunctioning and failures.
Therefore, there is yet an unfulfilled need for a device for controlling the trim of a boat, which can resolve the drawbacks of prior art devices.